1. Field of the Invention
The present invention relates to a slub yarn, in which a slub portion is formed by multiple windings of a sheath component around a core component, and a method and an apparatus for producing the same.
2. Description of the Related Art
Well known in the art are various slub yarns in which a slub portion is formed along a carrier portion (nonslub portion) by multiple windings of a sheath component around a core component by means of a false-twist texturing machine. For example, Japanese Examined Patent Publication (Kokoku) No. 55-22576 discloses a method for obtaining such slub yarn by feeding a sheath component to a core component in such a manner that the sheath component is positively traversed through a guide with a relatively longer period along the passage of the core component in a twisting zone of a false-twist texturing machine. The sheath component repeats a relatively shorter self-oscillation along the core component during the traverse motion. According to this method, since the sheath component is not fed at an overfeed rate sufficient to form a multilayered winding structure around the core component and the guide for the sheath component is maintained close to the core component, the resultant slub is relatively short and thin as well as of loose winding, though the shape thereof is of a typical fusiform. Regarding the apparatus proposed in this reference, since the yarn guide for the sheath component is driven by a power cylinder through a link mechanism, the traversing speed and distance thereof are limited to a lower level, so there are limited varieties of slub in the resultant yarn.
In Japanese Unexamined Patent Publication (Kokai) No. 58-109645, another slub yarn having a slub of a multiwinding structure is provided, in which an air-textured flat yarn is utilized as a sheath component and is fed to a core component in a manner similar to that of the abovesaid prior art method, except that the sheath component is sufficiently overfed but is not positively traversed along the core component. This method, however, has drawbacks in that the resultant slub has a deformed configuration because loops or fluffs inherent to the air-textured yarn protrude from a surface thereof. Moreover, a rigid slub having a multilayered winding structure of more than five layers cannot be easily obtained by this slub forming principle, as stated later.